The current mainstream method for securely transferring data between two apparatuses is to connect a data receiving apparatus to a server over a network, gain user authentication, and acquire conditions of use and a decryption key.
However, if the data receiving apparatus is installed in an ocean-going ship, the method of connecting the apparatus to a server over a network has a problem in convenience when transferring data. This is because the recent increase in download time because of delay due to the distance to satellite orbits and low communication speeds, economic performance, etc. hinders downloading a massive amount of files unlike an overland network, although the communication environment has been improved by the Internet over satellite. Furthermore, satellite communications do not always ensure communications because of the navigation area, weather, etc.
The above problem also applies not only to the case in which the data receiving apparatus is installed in an ocean-going ship but also to a case in which the apparatus is an apparatus installed in a high-speed mobile unit, which is difficult to satisfy both a communication band and economic performance, or the apparatus is a portable personal computer (PC) that may be used without power.